Donovan’s Vision Blog

Loading material from Reality Composer Pro scene

In this Jenga demo we have some orange coloured bricks. I thought it would be good to try to apply a material from one of the predefined examples in Reality Composer Pro.

Set up texture entity #

To begin we set up a primative (I chose a sphere) in Reality Composer Pro and add the MaplePlywood texture from the content library. Apply this texture, and name the sphere PieceTexture.

The PieceTexture object in Reality Composer Pro

Since we don't want this object to be visible or interact with anything, we won't add any connectors like collisions or physics. Instead we can add the Opacity connector, and set the opacity to 0%.

Setting opacity to zero

With that in place we now have an object in the scene from which we can load the texture in code.

Load material in code #

Before we load the texture, we can set up the following in the SharedViewModel. Add a new pieceMaterial variable, and then load the material using loadPieceMaterial inside the init method.

var pieceMaterial: RealityKit.Material?

init() {
    pieceMaterial = loadPieceMaterial(from: "Scene", named: "PieceTexture")
    generateTower()
}

With this we can put together some code to drive this loadPieceMaterial method.

Obtaining the material #

To obtain the material we want we need to set up a couple of helpful functions. First we need to find the entity.

Find the entity #

// Recursive function to search the entity and children for the named entity
func findEntity(named name: String, in entity: Entity) -> Entity? {
    if entity.name == name {
        return entity
    }

    for child in entity.children {
        if let foundEntity = findEntity(named: name, in: child) {
            return foundEntity
        }
    }

    return nil
}

This function when called will check entities and their children and then return the matching entity if found.

Find the material #

With the entity found, we check in a similar way to see if it is a component and return the first material, or else check the children and repeat.

// Finds a material from an entity (or its children)
func findMaterial(from entity: Entity) -> RealityKit.Material? {
    if let modelComponent = entity.components[ModelComponent.self] {
        return modelComponent.materials.first
    }

    for child in entity.children {
        if let material = findMaterial(from: child) {
            return material
        }
    }

    return nil
}

Putting the functions together #

Next we put these functions together to search for the entity, then the material, and return it.

func loadPieceMaterial(from sceneName: String, named materialName: String) -> RealityKit.Material? {
  guard let scene = try? Entity.load(named: sceneName, in: realityKitContentBundle) else {
      print("Error: Unable to load the scene.")
      return nil
  }

  if let materialEntity = findEntity(named: materialName, in: scene),
      let material = findMaterial(from: materialEntity) {
      return material
  } else {
      print("Error: Unable to find entity or its material in the scene.")
      return nil
  }
}

Applying texture to the brick pieces #

Lastly we want to update the code that applies the texture. In the generatePiece method amend the code that generates the piece to:

let piece: ModelEntity
let boxShape: MeshResource = .generateBox(width: pieceWidth, height: pieceHeight, depth: pieceDepth, cornerRadius: 0.005)
if let material = pieceMaterial {
    piece = ModelEntity(
        mesh: boxShape,
        materials: [material]
    )
} else {
    var defaultMaterial = PhysicallyBasedMaterial()
    defaultMaterial.baseColor.tint = .orange
    defaultMaterial.roughness = PhysicallyBasedMaterial.Roughness(floatLiteral: 1)

    piece = ModelEntity(
        mesh: boxShape,
        materials: [defaultMaterial]
    )
}

This will conditionally apply the material if loaded.

Textured blocks featuring a wooden material

That seems to work for now! I'd like to learn other hopefully more simple ways to load materials in Swift. I will update here once I learn more.